Prevalence of dementia in Europe

Prevalence of dementia

Methods

A Systematic review of papers reporting on the prevalence of dementia was performed. Using a Medline and Embase search we found a number of studies using the search terms “Dementia / Prevalence / Incidence / Epidemiology” or “Alzheimer’s Disease / Vascular dementia, Lewy-body disease/ Fronto-temporal dementia/ Incidence / Prevalence / Epidemiology. This was followed by hand searching these papers. A database of studies was compiled and those fulfilling predetermined quality criteria were invited to submit data for the collaborative analysis

Collaborative analysis

Inclusion criteria (Table 1) for involvement in the collaborative analysis were decided by the members of the EUROCODE prevalence working group. These were developed by consensual opinion looking at all methodological domains of this type of epidemiological study. Criteria were aimed to identify those studies of highest quality. Studies fulfilling criteria were invited to participate in the collaborative analysis. Age (by 5 year age group from 50 to >95years) and sex specific raw prevalence case numbers and underlying population were collected from all groups agreeing to participate in the collaborative analysis.

Table 1

Inclusion Criteria:

1. Community based study

2. Minimum sample size 300

3. Study survey date including 1990 or thereafter.

4. Use of standardized diagnostic criteria

5. Participation rate over 50%

6. Available raw prevalence data

Analysis

Age (5 year age range) and sex specific raw data from participating studies was included in the analysis. Data above 95 years was combined. Below this age raw data that could not be presented in 5 year age groups was excluded from the analysis. Age and sex specific prevalence’s were calculated using the total number of prevalence cases from all studies as the numerator and total population examined as the denominator. In this way weighting was achieved by each study’s sample size.

Results

A total of 194 articles were identified from the literature search. 31 studies were identified as possible for inclusion in collaborative analysis and they were invited to submit data. Raw data was obtained from 17 studies and used in the collaborative analysis of dementia prevalence rates in Europe. Table 2 outlines the 31 studies identified for participation and if not finally included the reason for non inclusion in yellow.

Table 2

Author

Year of publication

Year of Survey

Country

Reason for exclusion

Skoog

1993

1986-1987

Sweden

Too early

Roelands

1994

1990

Belgium

Raw data not available

Lobo

1995

1988-89

Spain

Too early

Manubens

1995

1991

Spain

Pouza

1995

Spain

Too small

Ott

1995

1990-93

Netherlands

Fichter

1995

1990

Germany

Raw data not available

Pi

1996

1992

Spain

Raw data not available

Prencipe

1996

1992-93

Italy

Andersen

1997

1994

Denmark

Ferini-Strambi

1997

1992

Italy

Obadia

1997

1991

France

Raw data not available

Boersma

1998

1991-92

Netherlands

Raw data not available

Azzimondi

1998

?

Italy

MRC FCAS (Liverpool)

1998

1989-91

UK

Too early

MRC FCAS (All other centres)

1998

1991-92

UK

Raw data not available

Strauss

1999

1992-1993

Sweden

Gabryelewicz

1999

1996

Poland

Vilalta-Franch

2000

1990

Spain

Cristina S

2001

1992-93

Italy

Low participation

Kurz

2001

?

Belgium

Not population based

Riedel-Heller

2001

1997-1998

Germany

Ravaglia

2002

1999-2000

Italy

Stevens

2002

1996-2000

England

Raw data not available

Gostynski

2002

1995-1996

Switzerland

Borjesson-hanson

2004

1998

Sweden

Tognoni

2005

2000

Italy

De Ronchi

2005

1991-1992

Italy

Helmer

2006

1998-99

France

Bdzan

2007

2002-2005

Poland

Lobo A

2007

1994-96

Spain

Raw data not available

Gascon-Bayarri

2007

2002

Spain

Prevalence rates from individual studies.

Table 3 shows the basic characteristics of each study included in the collaborative analysis with differences in geographical region, study size and age range of population evaluated.

Table 5

Total age specific prevalence rates were calculated by pooling data on prevalence case numbers and underlying population for males and females in each 5 year age range. Table 6 shows these rates

Table 6

Total Population - Age Range

Prevalence

60-64

0.6

65-69

1.6

70-74

3.5

75-79

7.4

80-84

15.7

85-89

26.2

90-94

41.0

>95

46.3

Comparison with previous data.

Figures 1 and 2 show graphically the comparison of the current data with that from the EURODEM project.

Figure 1

Figure 2

Discussion

From the current collaborative analysis it appears that for the majority of age groups dementia prevalence has not changed significantly over the last few decades despite the current analyses using completely new data from that included in EURODEM. Within the oldest old however dementia prevalence is higher in females and this level of prevalence has not been previously documented. This finding may be as a result of a higher proportion of studies reporting dementia prevalence in the older age ranges over the last 2 decades and probably reflects a true rate in this previously under reported population.

A comparative table of the estimated number of people with dementia (based on 2006 population statistics) was created by Alzheimer Europe after the end of the EuroCoDe study and can be found at:

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Prevalence of dementia

Acknowledgements

The EuroCoDe project received financial support from the European Commission. Neither the European Commission nor any person acting on its behalf is responsible for any use that might be made of the following information. Alzheimer Europe also gratefully acknowledges the support it received from Fondation Médéric Alzheimer for this project.